The invention concerns a process for selectively extracting dyestuffs contained in cyanophyceae algae, particularly algae of the Spirulina species.
It is known that the so-called "blue" algae (Cyanophyceae) particularly of the Spirulina species, contain a certain number of pigments in various proportions. They consist mainly of:
a green pigment: chlorophyll a, present in a proportion of about 0.1 to 0.15% of the weight of the dry algae;
a blue pigment: phycocyanine, present in a proportion of about 20 to 25% of the weight of the dry algae;
yellow, orange and red pigments: the carotenoids, present in a proportion of about 0.47 to 0.65% of the weight of the dry algae.
The extraction of chlorophyll is not of particular interest in the present case, since this pigment is often present in most of the plants.
On the contrary, the other pigments (blue, orange and red) are of high interest since they are not frequent in the nature. They may advantageously replace the synthetic dyestuffs used, up to now, in human and animal foodstuffs, certain of which are already prohibited or on the way to be prohibited, in view of their actual or suspected toxicity. The blue dyestuff is particularly interesting for use in human foodstuffs, in pharmaceuticals and cosmetics. It is, in fact, a blue protein wherein the phycocyanine pigment is completely bonded to the protein. The protein content of this blue dyestuff is about 65% by weight of the dry substance. Its aminogram is very similar to that of the algae which is used as raw material. This dyestuff is called hereinfter "phycocyanine".
It is already known that phycocyanine may be extracted from Cyanophyceae algae by contacting with an aqueous phase. As a matter of fact, phycocyanine diffuses in water when the algae cells are subjected to a certain lysis. This lysis may be obtained by re-suspending the algae in water, either after drying (for example by lyophilization), or after freezing or crushing of fresh algae.
When dry algae are used, the diffusion of phycocyanine is very slow. When starting from fresh algae, re-suspended after freezing or crushing, the lysing of algae cells is generally too high: the diffusion of the pigments is then poorly selective and the separation of the extract from the residual mass of algae is very difficult.